This invention relates to a fluoropolymeric composite material. More particularly, this invention relates to a fluoropolymeric composite material which is particularly well suited for use as a circuit board substrate material or as a bonding ply in a multilayer circuit board and in other applications requiring the ability to flow as well as good thermal, mechanical and electrical properties.
This application is related to U.S. application Ser. No. 483,502 (filed contemporaneously with this application) entitled DIELCTRIC COMPOSITE and invented by David J. Arthur, Gwo S. Swei and Phong X. Nguyen.
U.S. Pat. No. 4, 849,284 which is assigned to the assignee hereof and incorporated herein by reference describes a ceramic filled fluoropolymer-based electrical substrate material sold by Rogers Corporation under the trademark RO-2800. This electrical substrate material preferably comprises polytetrafluoroethylene filled with silica along with a small amount of microfiberglass. In an important feature of this material, the ceramic filler (silica) is coated with a silane coating material which renders the surface of the ceramic hydrophobic and provides improved tensile strength, peel strength and dimensional stability.
The ceramic filled fluoropolymer-based electrical substrate material of U.S. Pat. No. 4,849,284 is well suited for forming rigid printed wiring board substrate materials and exhibits improved electrical performance over other printed wiring board materials. Also, the low coefficients of thermal expansion and compliant nature of this electrical substrate material results in improved surface mount reliability and plated through-hole reliability. As is known, individual sheets of this electrical substrate material may be stacked to form a multilayer circuit board. In fact, thin film formulations of the material disclosed in U.S. Pat. No. 4,894,284 (and sold by Rogers Corporation under the trademark RO-2810) may be used as a bonding ply to bond together a plurality of stacked substrate layers so as to form the multilayer circuit board.
While the silane coating provides significant and unexpected features and excellent properties to the electrical substrate material of U.S. Pat. No. 4,849,284, there is nevertheless a perceived need to utilize additional and perhaps less costly filler coatings which would provide the same or better results as does the silane.